Residential buildings, automobiles, motorcycles, and the like include a lustrous element containing a metal thin film which is formed by evaporation, sputtering, wet-plating, or the like.
In order to form a metal thin film, for example, iron, aluminum, chromium, or the like is used. Among these metal thin films, a chromium thin film which is disclosed in Patent Document No. 1 has unique texture and excellent hardness and weatherability compared with the iron or aluminum thin film. Therefore, the chromium thin film has been widely used. The chromium thin film has excellent hardness and weatherability, therefore, it has not generally been used to form a coating film for protecting the chromium thin film.